Even Fire Crank

[Sparkroost]

Sounds easy enough.. What is it, or should I say, what is the advantage of an even fire crank? If it produces more power, what rpm range?

[Bill Gohr]

the even fire crank built for the crossflows would gain significantly in the mid-range and low end and almost nothing on top. You would see a gain in engine life.

[Sparkroost]

Tell me more! why don't they use them as standard? Can you convert a regular to even fire? What is the firing order. Talk to me Houston!

[ShipBear]

Even IF you could find one. You talking some $$$
Would be nice to have one..!!

Later Larry

[NEECAPR]

Bill and Bear, Can you describe how this crank is designed different from regular crossflows? Are they available for both 4 and 6 cylinders?

[BarryStrawn]

NEECAPR - Look at any OMC 90 degree V6 looper crank for an example. The rod journals for cylinders 1&2, 3&4 and 5&6 are offset so the engine fires at 0/60/120/180/240/300. The regular crossflow V6 fires at 0/90/120/210/240/330 because the rod journal pairs are lined up and the cylinders are 90 degrees apart.

All 90 degree V4s are inherently even fire because it fires every 90 degrees and the cylinder bank angle is also 90 degrees. I don't know what kind of crank is in the 60 degree Eagle V4.

I have no idea how this would make more low end or mid range power. It certainly would be smoother and help the engine live at high RPM which could be exploited for more power. Maybe Bill will explain the theory.

[NEECAPR]

Barry, Thanks for the info! I looked at an unfinished 6cyl. crossflow here and shame on me---I never noticed that the journal pairs line up-- not offset 30 deg. like the 6 cyl., 90 deg. looper. The four cyl., 60 deg. looper is offset 30 deg. the opposite way to get 90 deg. firing spacing. Incidentally, the Seloc Manual Vol. V for 1992-1996 Johnson/Evinrude shows a four cylinder crossflow in the exploded view that is labeled as a V-4 60 deg. loop charged powerhead. Not a real valuable book! As these timing spacings are varied, it seems that there would be variations in induction effectiveness at some speeds. Maybe this is why the better low and midrange.----Bill? :cool:

[BarryStrawn]

Originally posted by NEECAPR
it seems that there would be variations in induction effectiveness at some speeds. Maybe this is why the better low and midrange

Could be but I don't see how. The V6 exhaust operates as a pair of 120 degree 3 cylinders. Maybe a little interaction there at the ends of the tuner but I doubt it. On the inlet side there is no tuning between any cylinders that I can see. Other than getting rid of the shakes, I don't see anything. But Bill should know.

[Bill Gohr]

The even fire crank for 90 degree V-6 has offset journals. Thats why they are so hard to get. They didn't want to put them into production because we were coming out with the new 60 deg engines to replace the cross. The stock cross V-6 fires 90-30 (90+30=120X3=360 deg rotation) because of the journal placement and a 90 deg V, thats why we called them odd fire. When you move the journals back and fourth off the center the motor now fires every 60 deg making it an even fire engine. The newer 60 deg 6's are even fire because of the 60 deg V and 6 cyls (6X60=360 deg rotation)

Even fire cranks would give a significant gain in the mid-range, definately worth the money. Also, that noticeable cross flow sound is gone, going across the lake she sounds just like a Merc.
Every cross 6 I had, had a even fire in it. Its the only way to run them. My first pair of engines on my checkmate were big-bore 175's with cranks and 2.6 heads. Talk about motors with some grunt. You could trim the boat a little and punch it from a dead stop and get the whole boat out of the water.

[BarryStrawn]

OK Bill, we understand the configuration. But why does it make more midrange power? Or is this an old secret that you and Racer can't remember;)

[B.Leonard]

Sparky unless you've started running 235s all your v4s are even fire.

The odd fire 235 crank should be called a late fire crank because that is what is actually happening. The motor fires 123456 starting on the SB bank #1. After #1 fires #2 on the port bank fires next but on the odd fire crank it is delayed 30 degrees more than the even fire. This puts the #2 firing closer to the #3 firing back on the SB bank.

The exhaust pulses are still 120 apart within each bank for both cranks. However, if you tie the exhaust together (bypass hole or slot in the exhaust chest) the even fire has an advantage of "boosting" the other bank sooner (because it's not firing late like the odd fire crank). This may produce a better scavenging effect for the other bank that is not currently firing by keeping the exhaust moving in that bank whereas with the odd fire the exhaust would slow down in the non-firing bank more.

Just some thoughts from thinking about it a bit and talking to several people about them. This would explain why there is no top end increase because it only benefits low speed scavenging. Scavenging drastically improves on these motors with higher rpm (as with any 2 stroke) so it's not needed at higher rpm.

In my opinion it's not worth the money to run one since there are many other ways of improving low end responsiveness/power related to scavenging. One would be reducing crankcase volume. On the durability issue, just balance the motor and most durability issues will solve themselves regardless of what crank you're running.

Just my dumb ass opinion ;)

-BL

PS Almost forgot, the sound. Like Bill said they say the sound is worth the price alone. But now that my race 2.6 is running the odd fire sounds very similar to a Cup motor at idle with the high compression. No rhyme or rhythm at all :D

[NEECAPR]

Thanks all for the info. Never expected to see this on any engine.:eek: Regards Cy

[racer]

Bill I can remember can you? I think Barry is putting up a challange.

I would not say a significant difference but you could tell you had more power and the power was delivered in a much smoother fashion.

BL, as for no top end gain I will dissagree with that statement all day. The crank in itself did not help much but it did allow for other changes that did. It helped high rpm reliability a bunch. Balance is always a factor but with the even fire you can obtain a better balance. Since these engines fire every time they reach TDC the balance factors are totally different than a 4 stroke. Under 7200 the standard crank was not a problem with reliability but when we started to push that number up it was and the crank was a big help. I regularly turned an even fire engine over 8. You know from some of the stuff you bought from me we tried some different stuff on these engines.

As for why the mid improvement BL is in the right area.

[Bill Gohr]

is not mystical, when you have 2 three cylinder banks, of course they function better with the pulses being evenly spaced. The engine runnung smoother is the best advantage. I stated the hp gain is not neglidgable but the fact is the engine revs freer and will spin RPM's you will never see in its standard configuation. It may make slightly more hp at the top but the RPM gain and the hp being maintained at that RPM cannot be obtained without the crank. Of course this creates tuning situations that you will not see with an odd fire motor. There were also things we did in the intake tract that would work on the even fire engine that didn't work or not work as well on the odd fire engine.

Again, the biggest gain was in the mid-range, I heard numbers in the 20 to 25 HP range. When you add this with the added RPM advantage the motor would really work. You would run a taller prop because of the mid range and then carry the RPM's higher and get the big end.

Anyone who tells you the crank wasn't worth it just plainly couldn't afford it or never ran one. I don't care what you do to your cross flow, drop a crank in it and it will be better, period.

[Bill Gohr]

I can help you with your aging memory, However, this isn't a challenge......:D

[CUDA]

I paid my $2,700 for one back in 84-85, and told old Travlen Travis that I was getting it up into the high sevens, ( he would not believe me ) and it was staying together. Well I fliped it and never got to prove it.

[BarryStrawn]

OK, fair enough, you two can keep your secrets.:) I think I understand how 120 degree three cylinder tuning works which both the odd and even fire engines are. But if there are some magic intake or exhaust modifications added between the banks then I'll take your word for it.

I just always thought it was only the balance, smoothness, durability and resulting extended rev range.

Thanks

[B.Leonard]

There is an advantage to even firing placing less stress on the crank. When the pulses are wide it leaves more room for flexing.

However, the way the crank fires from top to bottom alone is prone to real flexing in itself so I can't say how bad a 30 degree delay could be. I don't think you could fire it differently since they all fire at every TDC.

-BL

[Forkin' Crazy]

So.....the timerbase is different too, right? Or, how would you time it?

:)

[Bill Gohr]

567704 only for that crank, How bout that racer boy......(Geritol race group.....land of fruits and nuts) remember that one?????

[Steve Pope]

What crank in a CCC. This was OMC hot motor. They would know what was bettrer????
Steve

[CDave]

So an even fire crank isn't the same thing as a 180 deg crank?

[racer]

The ccc was built before the even fire crank, they did have a harmonic balancer on the bottom of the crank.

[switzer]

Where can i get one of these cranks and what do they go for$

[aircraftman]

there are a couple out there. it took me over a year to find mine!!!! gold ! get yourself a flex flywheel also!!

BL 's new mota would be an animal with one!!! and dont say it wouldnt!:D

prob in the neighborhood of 1000- 2000 dollars with the timer base!!! and dont get one without the base!

[B.Leonard]

I'll pass :D

One of the things that is on the list for next years mods is cutting the crank counter weights down. With the bobb weight so light due to the lightweight pistons and rods, I can afford to cut the counter weights down a good bit. Decided to wait this year because so much has been changed as it is. You would never want to do that with a museum piece like that even fire crank (too rare).

Excess weight on the outer circumference of a rotating assembly kills aceleration big time. That is why the race flywheel which weighs close to a 10 amp stock wheel makes a noticable diff in acceleration. It weighs almost the same but it's weight is closer to center of rotation as opposed to the stock wheel which puts much of it's weight out by the starter gear.

-BL

[aircraftman]

you know you want one!!

how many hours you got on the project mota and have you spun it up yet??

if it makes it thru this year with the rumble and all im in for a couple sets of those pistons.

BTW - what pistons are in it weiscos or what?? and are they the 500g or 550g?
kris

[B.Leonard]

pistons Pro Marine (cast) - 550g
rods - 310g Cryoed/Polished
pins - 83g Taper cut
crank balanced but stock counter weight size.

It's been to 7200-7500 dozens of times. It's fine for lake/drag use. For enduro type use it might be a little light but who's gonna find out? :D

I'm gonna run Wisecos next time and they weigh in at 490g. We can go lighter on those because they're stronger (forged). Getting them Cryo'd and the tops coated to keep the heat off will help also.

-BL

[kennedyrd]

Hi all. I stumbled upon this old post, and wondered if the answer as to why the even fire crank boosted mid range power was a result of something Honda discovered in 1992. They were attempting to effectively reduce midrange power on their 500cc two stroke GP bikes to make them easier to ride, so they developed the "big bang" firing order. Basically making an inherently even fire engine odd fire! This was done to allow a long pause between firing pulses to allow the tire to recover traction between pulses, effectively a form of analogue traction control. Even in the 4 stroke Moto GP era this thinking still prevails.

Of course this isn't a problem when you have a propeller in water, and the increased midrange is then an advantage. Just an idea why the even fire crank worked so well. Could be completely wrong.

[loop]

I think it was mostly about reliability at higher rpms. All of OMC's crossflow V4 and V6 engines were 90 degree bank angle. This was perfect for the V4 but the not for the V6 which needs to be a 60 degree angle. The even fire crank basically corrected the odd firing with an offset crank pin. The later model 2.7, 3.0, 3.3, and 3.4 Loop charged V6's were also 90 degree but came with an even fire crank in all of them from the factory

[kennedyrd]

I think it was mostly about reliability at higher rpms. All of OMC's crossflow V4 and V6 engines were 90 degree bank angle. This was perfect for the V4 but the not for the V6 which needs to be a 60 degree angle. The even fire crank basically corrected the odd firing with an offset crank pin. The later model 2.7, 3.0, 3.3, and 3.4 Loop charged V6's were also 90 degree but came with an even fire crank in all of them from the factory

I am quite sure you are correct; I was just trying to explain the observation there was a massive gain in midrange from those who seemed to have experience with them. Ironically, when Honda campaigned the "big bang" engine, they had to replace the magnesium crankcases every race because the load from vibration was flogging out the cases! They subsequently switched to heavier aluminium cases when rules mandated a heavier weight limit anyway.

I loved the sound of even firing engines. I raced a Johnson Stinger GP KR15 in the early 90's and wished like hell I never sold it. I virtually gave it away, as the boat was taking up room. I should have just unbolted it and stashed it. I purchased that almost entirely for the sound! When the first V6's came in I was still a teenage boy and was disappointed in the sound they made after the V4's.

It is strange they went back to 90 degree bank angle in the loopers with the even firing crank to correct it. I didn't know that and wonder why they didn't stick with the 60 degree bank angle? It seems a much more elegant solution!

I assume the Mercury V6's remained odd firing as they don't "wail" like the even firing OMC's did.